Influence of barrier height and p-cladding layer on electroluminescent performance of AlGaN deep ultraviolet light-emitting diodes

The electroluminescent (EL) properties of AlGaN deep ultraviolet light-emitting diodes (DUV LEDs) are improved by increasing the Al composition of the barriers in the active region and decreasing the thickness of the p-cladding layer, respectively. Under 1.5 A cm(-2) direct current (DC) injection, the intensity of the parasitic peak around 320 nm is 43 times more than that of the band-to-band peak at 265 nm in the LED with a lower Al-composition (55%) barrier, while the parasitic peak is suppressed efficiently in the LED with a higher Al-composition (70%) barrier. By increasing the Al composition from 55% to 70% and decreasing the thickness of the p-cladding layer from 25 to 10 nm, the light output power of the DUV LEDs improved 305 and 61 times at DC injection of 1.5 and 15 A cm(-2), respectively. The band structure and the vertical conductivity were calculated. It was found that the increase of Al composition not only enhanced the barrier height for quantum wells but also decreased the barrier for hole injection. On the other hand, the thickness decrease of p-type cladding layers to some extent resulted in the improvement of both hole concentration and vertical tunneling conductivity. All of these contributed to the improvement of the EL properties of the LEDs.